<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <link rel="stylesheet" href="./css/style.css">
</head>
<body>
  
  <div class="box">box盒子</div>
  <p>我是内容</p>

  <script src="./js/test.js"></script>
  <button>修改box</button>

  <script>

    var boxEl = document.querySelector(".box")
    var btnEl = document.querySelector("button")
    btnEl.onclick = function() {
      // boxEl.remove()
      boxEl.style.height = "200px"
    }


    function sum(num1, num2) {
      return num1 + num2
    }

    sum(20, 30)
    sum(20, 30)
    sum(20, 30)
    sum(20, 30)
    sum("abc", "cba")

  </script>
</body>
</html>